OBJECTIVES
There is limited evidence on costs associated with ipilimumab. We investigated healthcare costs of ipilimumab treatment in Dutch patients with advanced cutaneous melanoma and compared costs across subgroups.

METHODS
Data were retrieved from the nation-wide Dutch Melanoma Treatment Registry for patients diagnosed between July 2012 and July 2015. Ipilimumab episode duration was computed from start of ipilimumab until start of a next systemic treatment, death, or last date of follow-up. Costs were determined by applying unit costs to individual patient resource use. Patient subgroups were stratified by experiencing an immune related adverse event (irAE): no irAE, colitis, and irAE other than colitis.

RESULTS
A total of 807 patients received ipilimumab in Dutch clinical practice. Baseline characteristics were comparable across subgroups. Mean [median] episode duration was 6.27 [4.61] months. Average total healthcare costs amounted to €81,484, but varied widely (range: €18,131-€160,002). Ipilimumab was the most important cost driver (€73,739; 90.5%). Most patients (65%) received 4 cycles of ipilimumab (average dosage: 240mg [SD:45.6mg]). Other healthcare costs (€7,745) were related to hospital admissions (€3,323), hospital visits (€1.791), diagnostics and imaging (€1,505), radiotherapy (€828), and surgery (€297). Although patients with colitis (n=106) had higher costs for resource use other than ipilimumab (€11,426) compared to patients with other types of irAEs (n=90; €9,850) and patients with no irAE (n=611; €6,796), they had lower total costs (€76,075 versus €87,882 and €81,480, respectively) due to less cycles of ipilimumab. Patients with an irAE other than colitis had a longer (mean [median]) episode duration (7.96 [6.38] months) compared to patients with colitis (6.91 [4.92] months) and patients with no irAE (5.92 [4.28] months).

CONCLUSIONS
Healthcare costs associated with ipililumab treatment are considerable in Dutch patients with advanced cutaneous melanoma. Although costs were mainly related to drug costs of ipilimumab, total costs and the distribution of the costs varied significantly across subgroups.